Klystron tube



1960 G. K. MERDINIAN 2 ,949,559

KLYSTRON TUBE Filed Jan. 31, 1958 3 Sheets-$heet 1 1 I I GEORGE K.MERDINIAN INVENTOR.

ATTORNEY 1 G. K. MERDINIAN 2,949,559

KLYSTRON TUBE Filed Jan. 31, 1958 9 3 Sheetsdheet 2 GEORGE K. MERDINIANINVENTOR.

FIG. 3

-ATTORNEY G. K. MERDINIAN 2,949,559

KLYSTRON TUBE Aug. 16, 1960 Filed Jan. 51, 1958 3 Sheets-Sheet 3 ill:

FIG. 4

' FIG.5

F I G. IO

FIG. 9

FIG. 8.

INVENTOR.

GEORGE K. MERDINIAN Fl G. 7

MFW'

ATTORNEY KLYSTRON TUBE George K. Merdinian, Daly City, Calif., assignorto Eitel- McCullough, Inc., San Bruno, Calif., a corporation ofCalifornia Filed .Ian. 31, 1958, Ser. No. 712,354

Claims. (Cl. 315-546) This invention relates generally to a klystrontube and more particularly to a klystron tube having an improved outputcavity resonator, and improved means for coupling to a waveguide outputcircuit.

One of the problems encountered in klystron tubes is that of efiicientlycoupling energy from the output cavity. When operating at a particularpower output and a relatively narrow band of frequencies, it is possibleto design a coupling means which optimizes the degree of couplingbetween thte cavity and associated output circuit. However, when it isdesired to operate a klystron tube over a relatively wide range offrequencies with variable power outputs, a fixed coupling of the abovecharacter is unsatisfactory.

Waveguide transmission circuits are capable of handling more power andintroduce less power loss per unit length than are coaxial transmissioncircuits. Thus, in many applications it is desirable to connectwaveguide transmission circuits directly to a cavity resonator, forexample, the output cavity resonator of a klystron tube.

One type of klystron tube includes resonant cavities having two parts: apart which forms a portion of the evacuated envelope, and another partwhich carries the tuning means. The two parts are coupled togetherthrough a dielectric window. It is necessary to operate this type oftube in such a manner that the window does not overheat or it may crack,destroying the vacuum. When the energy in the cavity is not properlycoupled out, the window may reach dangerously high temperatures.

It is a general object of the present invent-ion to provide a klystrontube with improved waveguide coupling.

It is another object of the present invention to provide a cavityresonator for a klystron tube with waveguide transmission line inputand/ or output.

It is a further object of the present invention to provide improvedcoupling between a cavity resonator and a waveguide transmissioncircuit.

It is another object of the present invention to provide an outputcavity resonator having an adjustable degree of coupling to associatedapparatus.

It is another object of the present invention to provide an adjustableiris diaphragm coupling between a cavity resonator and associatedapparatus.

It is another object of the present invention to provide a cavityresonator which is tunable over a relatively broad range of frequencies.

It is another object of the present invention to provide a tunablecavity resonator which may be air cooled thereby operating the couplingwindow at lower temperatures.

It is a still further object of this invention to provide a variablewave guide circuit element.

These and other objects of the invention will become more clearlyapparent from the following description when taken in conjunction withthe accompanying drawings.

=Refen'ing to the drawing:

nited States Figure 1 is an elevational view, partly in section, of athree-cavity klystron tube;

Figure 2 is a sectional view taken along the lines 2-2 of Figure 1 andshowing the tuning plungers and improved coupling;

Figure 3 is a sectional view taken along the lines 3--3 of Figure 1;

Figure 4 is an end view of a suitable tuning plunger;

Figure 5 is a side elevational view, partly in section, of the tuningplunger of Figure 4;

Figure 6 is a sectional view taken along the line 6-6 of Figure 2showing the adjustable iris diaphragm in elevation;

Figure 7 is a sectional view taken along the line 7-7 of Figure 2showing one of the iris diaphragm plates; and

Figures 8-10 show various means for making electrical contacts betweenthe iris diaphragm plates and the cavity resonator walls.

Referring to Figure l of the drawing, a klystron tube with tuningchambers and coupling means according to the subject invention isillustrated. The tube comprises an elongated generally cylindricalenvelope having an electron gun 11 at one end and a collector electrode12 at its other end. The electron beam is projected from the electrongun to the collector and passes through a drift tube made up of metallicsections 13, 14, 15 and 16 which extend axially of the tube and havethree gaps, of which 17 is shown. Such gaps are bridged by tuningchamber structures. Three chambers 18, 19 and 20 are shown associatedwith the gaps.

The tuning chambers are made up of two parts; an inner portion which isstructurally integral with the envelope and forms a portion of theevacuated envelope, and an outer portion which is external to theevacuated envelope. Dielectric windows 22, one of which is shown, formportions of the envelope and provide means for coupling energy from theinternal evacuated portions of the resonant cavities to the portionswhich are external of the vacuum envelope. The windows surround theassociated gaps and have their ends 23 and 24 sealed to adjacent plates26 and 27 which form a part of the evacuated envelope and which may alsoform a part of the resonant cavity. Tuning means 25 are carried in theexternal portions of the tuning chambers.

The above described elements of the tube function in a manner well knownfor klystron tubes of this type, name ly, an electron beam from the gun11 is accelerated by a positive potential on its anode (not shown) andpasses through the drift tube past the interaction spaces provided bythe gaps, and finally terminating on the collector 12. The associatedtuning chambers 18, 19 and 20 serve as the frequency determiningelements of the device. As previously described, the tuning chamberscontain movable tuning means which serve to tune the cavity over aparticular frequency range. The tube illustrated may function as anamplifier with the input signal for modulating the electron beam fedinto the resonant cavity 18 and the amplified radio frequency outputtaken from the resonator 20 in accordance with the usual practice in athree-cavity type klystron.

The resonant cavities are formed by the plates 26 and 27, extensionplates 26a and 27a being suitably secured thereto. As shown in Figure 2,the output cavity 20 comprises a side wall 28 suitably secured to thespaced end walls, and wall portions 29 and 31 which extend towards oneanother. The adjacent ends of the wall portions 29 and 31 are taperedand spaced from one another to provide a fixed opening through which themicrowave energy within the cavity resonator may be coupled toassociated apparatus. 'It is observed that the klystron and cavityresonator described are formed as a unitary structure.

However, it will be apparent from the description which follows that theinvention is not to be limited in this respect. The external portion ofthe cavity may be formed as a separate assembly which is suitablyclamped to the klystron for operation therewith. Klystrons of this typeare well known in the art.

The output cavity is adapted to be coupled to a waveguide transmissioncircuit. Thus, a section of waveguide 34 provided with connectingflanges 35 is suitably secured to the adjacent wall portions 29 and 31and the end walls 26 and 27. A waveguide may then be suitably attachedto the flanges 35.

Energy is coupled to associated apparatus through the adjustable irisopening 37. The iris illustrated is an inductive iris; however, it willbecome apparent that a capacitive iris may be employed if desired. Thearea of the opening 37 may be controlled by moving the adjustablediaphragms 38 and 39. In Figure 6, the diaphragrns 38 and 39 are shownin elevation. An edge of each of the diaphragms is provided with teeth41, 42 which engage an adjacent threaded worm-screw 43, 44,respectively. The screws 43 and 44 are threaded in an opposite sensewhereby rotation of the shaft 46 which is coupled to the screws 43 and44 urges the diaphragms 38 and 39 in opposite directions. Thus, byrotating the shaft 46, the diaphragms 38 and 39 are moved symmetricallytowards or away from one another to thereby control the width of theiris opening 37.

The diaphragms 38 and 39 are guided in the grooves 47 and 48 formed inthe plates 26 and 27. The side edges of the diaphragms 38 and 39 areprovided with suitable means for making electrical contact in thegrooves. For example, the side portions may be serrated and bent to forma series of fingers 51 which engage opposite sides of the grooves asindicated in Figures 7 and 8. The diaphragms 38 and 39 may be providedwith finger contacts 52 and 53 as indicated in Figure 9, whichfrictionally engage the sides of the groove to provide an electricalcontact and guide the diaphragm. Alternatively, the side edges of thediaphragms may extend into the slot 47 which is filled with metallicmaterial 55 which makes electrical contact therewith as shown in Figure10. A pair of adjustable plates 54 and 56 is secured to the wall andguides the diaphragm. It is apparent that other means may be employedfor guiding the diaphragms 38 and 39 and providing electrical contact.

The diaphragm 38 is guided between the plates 26 and 27 by means of thepins 57 which extend inwardly from the wall 29 while the diaphragm 39 isguided by the pins 58 which extend inwardly from the wall 31. These pinsmay be the screws 57 and 58 (Figure 2) which engage one end of the webmembers 63 and 64. The screws 61 and 62 extend inwardly and engage theother end of the web members 63 and 64. The web members 63 and 64receive the adjusting screws 68 and 69 associated with the tuningplungers 71 and 72, to be presently described. The open construction ofthe web members makes it possible to blow air through the resonantcavity past the dielectric window to thereby cool the same.

The diaphragms 38 and 39 are also guided by the guides 73 and 74 whichare carried on one face thereof and which are adapted to ride withinaccommodating slots 76 formed in the adjacent side wall portions 29 or31.

Each of the tuning plungers is of box-like construction (as viewed fromthe end) comprising four walls; the side walls 77, 78, 79 and 80. Thewalls are carried by a frame 81. A strap 82 extends across the frame andreceives the end of the associated tuning screw 68 or 69. The end of thetuning screw is rotatably received by the associated strap S2. Forexample, the arrangement might comprise a collar 83 carried on the screw68 which collar is seated within an annular groove 34. Thus, rotativemovement of the screw 68 moves the tuning plunger.

The tuning plunger is provided with a plurality of contact fingers 85which are suitably secured to side walls of the plunger and whichfrictionally engage the adjacent wall portions of the resonant cavity.Referring particularly to Figures 1 and 2, the'contact fingersfritctionally engage the walls 26 and Z7, and the side wall 28, and thediaphragms 38 and 39. Thus, electrical contact is made between thetuning plunger and the adjacent wall portions. The walls 77 and 79 havean end configuration which has a straight portion '87 which extendssubstantially at right angles to the side, a curved portion 88, and arelatively straight portion 89 which forms a continuation of the curvedportion. The curved portion has the configuration of the window wherebywhen a pair of plungers is moved inwardly, they surround the window toform a relatively small resonant volume. If, on the other hand, theplungers had a straight end, the volume of the cavity could not bereduced to as small a volume and, therefore, the upper resonantfrequency would be much lower. Because of the curved configuration, thetuning cavity may be tuned over a relatively wide range. The straightportion 89 lies adjacent the iris opening 37 whereby when the tuningplungers are moved towards one another they will not block the irisopening '37.

The exact configuration of the ends of the walls 77 and 79 may bearrived at by trial and error to achieve the smallest cavity volume andbest coupling techniques, if desired. In general, as previouslydescribed, this can be achieved by walls having straight portions 87, acurved portion 88 which is adapted to fit around the window, and astraight portion 89 which forms a smooth continuation of the curvedportion.

A screen mesh 86 is suitably secured to the forward end of the walls 77,78, 79 and .to form the end wall. The open box-like configuration of theplungers and the screen mesh provide a means for circulating air throughthe cavity to cool the window.

The degree of coupling between the resonant cavity and the associatedwaveguide or to any other microwave transmission line or device isapproximately proportional to the width of the iris. The required degreeof coupling is, in general, dependent upon the amount of energy storedin the resonant cavity which is available for a load. It is oftendesirable to be able to adjust this coupling for optimum power output.This depends both upon the power output and the frequency of operationand, therefore, by providing an adjustable iris opening the greatestefiiciency over the widest range of power outputs and frequencies may beobtained.

A suitable dial indicator may be coupled to the screws 43 and 44. Acalibration for various outputs and he quencies may be obtained wherebythe screws may be turned so that when the indicator dial is set to apredetermined value the most efficient coupling is obtained.

It is observed that the iris opening is symmetrical with respect to theaxis of the tube, and the tuning means are formed symmetrical also. Thisprovides a symmetrical field within the cavity and means symmetricallycoupling thereto to give improved frequency characteristics to thecavity.

Thus, it is seen that there is provided a cavity resonator which can betuned over a relatively broad band of frequencies with a noveladjustable waveguide coupling means therefor. The novel coupling meansmakes it possible to efiiciently couple energy out of the resonator intoa Waveguide transmission system over a relatively broad band offrequencies and range of powers. There is also provided a klystron tubewith improved waveguide coupling.

The novel coupling means according to this invention may also 'beadapted for use as a variable wave guide circuit element independentlyof a resonant cavity or of a klystron tube. For example, it may bedmirable to provide inductive or capacitive diaphragrns according tothis invention in a wave guide circuit interconnecting microwaveapparatus so that such apparatus may be matched to each other byintroducing the proper amount of E lumped inductance or capacitance intothe interconnecting wave guide, the amount of reactance introduced intothe wave guide being varied by varying the degree of insertion of thediaphragms into the wave guide.

I claim:

1. In combination, an electron tube and a cavity resonator, said cavityresonator including means for connecting a waveguide transmission systemthereto, an opening formed in said resonator adapted to communicate withthe associated waveguide transmission system, a pair of movablediaphragms serving to control the size of the opening, and means formoving said diaphragms simultaneously towards and away from one another,said movable diaphragms forming an adjustable iris for coupling theresonator to the associated Waveguide transmission system.

2. A klystron tube comprising an electron gun serving to project anelectron beam, a collector spaced from said gun and disposed to receivesaid beam, an input cavity resonator coupled to said beam and serving tobunch the same, an output cavity resonator coupled to said beam andadapted to be excited thereby, means for coupling said output cavityresonator to an associated Waveguide circuit, said means including anadjustable iris having a pair of movable diaph-ragrns, and means formoving said diaphragms simultaneously towards and away from one anotherto thereby control the size of the iris opening.

3. A klystron tube comprising an electron gun serving to project anelectron beam, a collector spaced from said gun and adapted to interceptsaid beam, a drift tube including a plurality of sections forming atleast first and second gaps, an input cavity resonator associated withsaid first gap serving to bunch the beam, an output cavity resonatorassociated with said second gap and adapted to be excited by theelectron beam, means for connecting a waveguide transmission system tosaid output cavity resonator, an opening formed in said output cavityresonator adapted to communicate with the associated waveguide system, apair of movable diaphragms serving to control the width of the opening,and means for moving said diaphragms simultaneously towards and awayfrom one another, said movable diaphragms forming an adjustable iris forcoupling the resonator to the associated Waveguide transmission system.

4. A klystron tube of the type which includes an evacuated envelopeportion and external resonator portions comprising an electron gunserving to project an electron beam, a collector spaced from said gunand adapted to intercept said beam, a drift tube including a pluralityof sections forming at least first and second gaps, a plurality ofwindows each surrounding one of said gaps and forming a part of theevacuated envelope, an input cavity resonator serving to excite the beamat said first gap, an output cavity resonator adapted to be excited bythe beam at said second gap, means for connecting said output cavityresonator to an associated waveguide circuit, an adjustable iris havinga pair of movable diaphragms between said output cavity resonator andsaid waveguide circuit, and means for moving said diaphragmssimultaneously towards and away from one another to control the width ofthe iris opening to thereby control the coupling between the resonantcavity and associated waveguide transmission circuit.

5. A klystron tube of the type which includes an evacuated envelopeportion and external resonator portions comprising an electron gunserving to project a beam of electrons, a collector spaced from said gunand adapted to intercept said beam, a drift tube including a pluralityof sections forming a plurality of gaps, one of said gaps serving as anoutput gap, a pair of spaced parallel plates disposed on either side ofsaid output gap, a window surrounding said gap and forming a vacuum sealwith said plates, means cooperating with said plates and forming atunable resonant cavity, means for connecting said d resonant cavity toan associated waveguide circuit, and an adjustable iris opening betweensaid tunable resonant cavity and said waveguide serving to couple energyfrom the cavity to the associated waveguide circuit.

6. A klystron tube of the type which includes an evacuated envelopeportion and external resonator portions comprising an electron gunserving to project a beam of electrons, a collector spaced from said gunand adapted to intercept said beam, a drift tube including a pluralityof sections forming a plurality of gaps, one of said gaps serving as anoutput gap, a pair of spaced parallel plates disposed on either side ofsaid gap, a window surrounding said gap and forming a vacuum seal withsaid plates, means cooperating with said plates and forming a tunableresonant cavity, means for connecting said resonant cavity to anassociated waveguide circuit, an opening formed in said resonant cavityadapted to communicate with said associated waveguide circuit, a pair ofmovable diaphragms serving to control the width of the opening, andmeans for moving said diaphragrns simultaneously and symmetricallytowards and away from one another, said movable diaphragms forming anadjustable iris adapted to couple the resonant cavity to the associatedwaveguide circuit.

7. In combination, an electron tube and a rectangular cavity resonator,said rectangular cavity resonator including means for connecting awaveguide transmission system thereto, an opening formed in one wall ofsaid resonator adapted to communicate with an associated waveguidetransmission system, a pair of movable diaphragms serving to control thewidth of the opening, means for moving said diaphragrns simultaneouslytoward and away from one another, said movable diaphragms forming anadjustable iris for coupling the resonator to the associated waveguidetransmission system, a pair of tuning plungers making sliding contactwith the walls of said cavity resonator, each of said plungers havingcooperating opposed surfaces, said surfaces having a first straightportion, a curved portion, and a second straight portion forming acontinuation of said curved portion, said last named straight portionextending to the wall of the cavity including said opening whereby saidplungers do not interfere with the adjustable iris opening.

8. A klystron tube comprising an electron gun serving to project anelectron beam, a collector spaced from said gun and disposed to receivesaid beam, an input cavity resonator coupled to said beam and serving tobunch the same, a rectangular output cavity resonator coupled to saidbeam and adapted to be excited thereby, means for coupling said outputcavity resonator to an associated waveguide circuit, said meansincluding an adjustable iris having a pair of movable diaphragrnsbetween said output cavity resonator and said waveguide circuit, andmeans for moving said diaphragms simultaneously and symmetrically towardand away from one another to thereby control the Width of the irisopening, and a pair of tuning plungers making sliding contact with theWalls of said cavity, each of said plungers having opposed cooperatingsurfaces including a first straight portion, a curved portion and asecond straight portion forming a continuation of said curved portionand extending toward the iris opening.

9. A klystron tube of the type which includes an evacuated envelopeportion and external resonator portions comprising an electron gunserving to project an electron beam, a collector spaced from said gunand adapted to intercept said beam, a drift tube including a pluralityof sections forming at least first and second gaps, a plurality ofwindows each surrounding one of said gaps and forming a part of theevacuated envelope, an input cavity resonator serving to excite the beamat the first gap, an output cavity resonator adapted to be excited bythe beam at the second gap, means for connecting said output resonantcavity to an associated waveguide circuit, an adjustable iris openinghaving a pair of movable 7 diaphragms between said output cavityresonator and said waveguide circuit, means for moving said diaphragrnssimultaneously toward and away from one another to control the width ofthe iris opening to thereby control the coupling between the resonantcavity and associated waveguide transmission circuit, and a pair oftuning plungers making sliding contact with the walls of said outputresonant cavity, each of said plungers having co operating surfaces,said surfaces having a first straight portion, a curved portion adaptedto surround said window and a second straight portion forming acontinuation of the curved portion and extending toward the iris open-10. A klystron tube comprising an electron gun serving to project anelectron beam, a collector spaced from said gun and adapted to interceptsaid beam, a drift tube including a plurality of sections forming atleast first and second gaps, said second gap forming the output gap, apair of spaced parallel plates disposed on each side of said output gap,a window surrounding said gap and forming a vacuumseal with said plates,side walls connected to said plates, a pair of tuning plungers makingsliding contact with said plates and side walls, eachof said plungershaving opposed cooperating surfaces, said sur-. faces having a firststraight portion, a curved portion adapted to surround said window, anda second straight portion forming a continuation of said curved portion,and adjustable iris coupling means adapted to couple energy form thecavity formed by said plates and said sidewalls to an associatedWaveguide circuit.

References Cited in the file of this patent UNITED STATES PATENTS2,394,008 Pierce Feb. 5, 1946 2,410,109 Schelleng Oct. 29, 19462,579,327 Lund Dec. 18, 1951 2,588,262 Matare Mar. 4, 1952 2,629,066Eitel Feb. 17, 1953 2,629,774 Longacre Feb. 24, 1953 2,724,805 SntullinNov. 22, 1955 2,798,184 Gardner et al. July 2, 1957 2,834,949 Duffy May13, 1958 2,837,686 Drieschman et al. June 3, 1958 2,865,009 Litton Dec.16, 1958

